The present invention relates to photographic-quality prints, including non-photographic methods for making such prints.
Photography provides an easy and reliable way to permanently capture images for a variety of uses. While photographs provide durable images, they are prone to scratches; have poor resistance to light and ultraviolet radiation (which causes photographic images to fade over time), and degrade when exposed to water. Traditional photography uses harsh and expensive chemicals, requires silver recovery, and involves a process requiring several intermediate steps of handling negatives. While photographic processes can be automated, such automatic processing machines are expensive and bulky and do not eliminate the inherent problems of chemical exposure and handling negatives. Additionally, producing large prints (larger than the traditional 3-by-5 inch or 4-by-6 inch prints) can be quite expensive.
Digital photography and imaging provide cost-effective alternatives for capturing images, but known methods of producing durable, hardcopy prints of digital images are at least as expensive as traditional photographic methods. Images may be printed on paper using inkjet or electrostatic methods. With increasing use of various printing and imaging technologies in the publishing industry as well as in the home, protecting imaged or printed documents against abrasion, water or alcohol spills, ink smear, or other image-degradation processes and effects has become an important consideration. Such protection is particularly desirable for printed or imaged documents produced with water-based or water-soluble inks, or other liquid inks. These inks are commonly used in ink-jet printing, offset printing, and the like.
Hot and cold laminates are the most common methods used to protect images. However, laminates tend to be expensive, typically costing 6 to 80 cents per square foot for materials. The labor-intensive nature of producing durable prints via lamination also increases the cost of such prints.
Laminates may be applied on one or both surfaces of the print. One-sided lamination may lead to excessive curling of the final print, whereas two-sided application can be very expensive in terms of material and labor costs and may excessively increase the thickness of the final print.
Adhesives used for cold laminates may be tacky at room temperature, leaving a sticky residue at the edges of the prints. Additionally, binders used in creating cold laminates are typically water-based, which means the print may delaminate if exposed to excessive water.
Lamination is also susceptible to trapped air pockets, which are viewed as image defects. Most importantly, care must be taken to ensure that the layers of such laminates are accurately aligned to the base media, and such alignment is especially critical for a continuous web laminate. These are just some of the deficiencies of traditional laminates.
Liquid overcoats are commonly used to protect photographic prints and are becoming more popular as protective coatings for inkjet images. Typical systems for applying these overcoats rely on roller coating or gravure type systems to dispense, gauge, and apply the coating. Smaller systems typically apply the overcoat off-line, rather than being an integral part of a single printing and coating unit. Larger systems used by the printing industry are in-line, but require extensive monitoring. Both systems require significant manual cleaning or intervention to maintain the components that contact the liquid.
These liquid overcoats tend to be slightly less expensive than laminates (6-18 cents per square foot). However, because currently available systems must be cleaned frequently and regularly monitored, these methods of using liquid overcoats are just as labor-intensive as the lamination methods, if not more labor-intensive. Additionally, many of the overcoat formulations have residual odors before and/or after application, and some people find these odors offensive or even harmful.
Ultraviolet (UV) light curable liquid overcoats are also available, such as the overcoats commonly used to protect magazine covers. In such a UV-curable system, the liquid is first applied to the surface of the print and then cured to yield a solid, durable, protective coating. Because these liquids are widely used in large volumes for the magazine industry, their cost tends to be significantly lower than most other overcoat options. However, the systems used to apply such UV-curable overcoats tend to be more complicated and costly than other liquid overcoat systems, due to the multi-step application and cure process. Additionally, many of the overcoat formulations have strong odors, some of which are harmful or offensive to people.
Durable digital prints may also be created using a three-layer product made from (1) a transparent carrier as a substrate for an image; (2) an image; and (3) a white opaque laminate backing. Rather than viewing the printed surface directly, or viewing it through an applied clear protective coat, these prints are viewed through the backside of the clear substrate. The undercoat applied to the printed surface provides a white opaque background for the image. Cherian""s U.S. Pat. No. 5,337,132 discloses such a three-layered print involving the use of a transparent polyester substrate for receiving a toner image and a solid, opaque backing member which is adhered to the imaged surface (much like a laminated sheet). An off-line heat press is used to adhere the backing to the imaged substrate; however, the backing member must be manually positioned and aligned in the press before the adhesion step.
Another example of a three-layer digital print is disclosed in Coleman et al.""s U.S. Pat. No. 5,327,201, which describes a less labor-intensive method of applying the white backing. In this invention, an off-line applicator is used to carefully register a solid backing member to a carrier before gluing the two together. Malhotra et al.""s U.S. Pat. No. 5,795,695 also discloses, in greater detail, the transparent substrates, backings, and performance improvement additives which may be used in such methods of producing such three-layer digital images.
Electrophotography utilizes powdered thermoplastic particles, generally called xe2x80x9ctoner,xe2x80x9d to create images on media. Electrophotography typically involves the steps of: (1) forming a charged electrostatic charge pattern on an intermediary surface; (2) oppositely charging toner particles; (3) adhering the toner particles to the charged pattern on the intermediary surface; (4) transferring the toner particles from the intermediary surface to a receiving media (typically paper); and (5) fusing the toner particles to the receiving media with heat and pressure to coalesce them and adhere them to the surface. Detailed descriptions of electrophotography can be found in Schein, Electro-photography and Development Physics, 2nd Ed., 1992, Springer-Verlag.
Similar electrostatic methods are also commonly used in the commercial painting industry to powder coat products, parts, or assemblies. One powder coating method charges a powdered paint using an air gun outfitted with an electrode before spraying the charged paint onto an electrically grounded object. Alternatively, an electrically grounded object may be immersed in a charged, fluidized bed of paint particles (typically referred to as xe2x80x9cfluidized bed powder coatingxe2x80x9d).
The present invention addresses the needs described above. Inexpensive photographic-quality prints, methods for creating such photographic-quality prints, and an apparatus for producing these prints are described.
These photographic-quality prints generally comprise three layers: a transparent carrier as a substrate for receiving an image; an image; and a particle-based undercoat. The transparent carrier may include materials which increase adhesion to inkjet dyes or pigments, increase resistance to scratches, increase resistance to fading, increase resistance to moisture, increase resistance to UV light, or provide a matte, texture, or gloss. The transparent carrier generally comprises a square or rectangular sheet, though the shape of the carrier is not limited in any way, and the size and thickness of the carrier may vary.
The image can be provided to the carrier using commonly known and available means, such as inkjet printing, electrostatic methods, and other imaging methods. In some embodiments, the image is reverse printed to the transparent carrier, forming a mirror image. A particle-based undercoat generally covers the printed surface and, once fused, protects the printed area, providing a solid-fill, reflective background.
Thus, a photographic-quality print of the present invention can be understood as an image sandwiched between two protective layersxe2x80x94a transparent carrier and a particle-based undercoat. In such an embodiment, the viewer looks at the image through the transparent carrier surface opposite the printed surface.
The particle-based undercoat is applied to the same side of the carrier as the image. Application of the particle-based undercoat, rather than a solid laminate layer, solves problems inherent in the known prior art, such as avoiding a critical need for aligning solid laminate members. Particle-based undercoats of the present invention are generally less expensive than solid laminates and also avoid problems caused by air pockets trapped under solid laminates. Methods of the present invention for applying particle-based undercoats are also less labor-intensive than known methods of protecting digital images, such as using laminates or liquid overcoats.
A particle-based undercoat such as an opaque white powdercoat, toner, pigment, or powdered plastic resin may be used. The particle-based undercoat may be applied to the transparent carrier in a single step, or the undercoat may be first provided to the carrier and then affixed to the carrier. The particle-based undercoat may be applied to form a layer of uniform or non-uniform thickness across the transparent carrier. Different shades of white, or alternate colors of undercoat, or a transparent undercoat, may be used to alter the appearance of the prints.
The particle-based undercoat may also include materials that increase the adhesion to inkjet dyes or pigments, increase adhesion to the carrier medium, increase resistance to scratches, increase resistance to fading, increase resistance to moisture, increase resistance to UV light, provide a smudge resistant finish, provide a scuff resistant finish, or have similar rheological and mechanical properties as the transparent media.
An apparatus embodying methods of the present invention is also described. The apparatus comprises an imager for providing an image to the transparent carrier and a particle-based undercoat module for applying and affixing the particle-based undercoat to the transparent carrier.